The geology of the Basement varies from house to house should a building actually house what is commonly referred to as the basement. Often these basements will be man made features, although the original and oldest basement is thought to be a cave in northwest Scotland.
The original geological basement is a natural freshwater cave in the northwest of Scotland formed entirely within Cambro-Ordovician carbonate sediments. Through misinterpretation of geological literature however, geologists have often thought that this term basement refers to the underlying crystalline rock (also known as Lewisian Gneiss) which underlies these carbonates. Several famous geologists such as Peach, Horne and Nicol were happy to acknowledge their early mistake regarding this, although university professors and postgraduates worldwide still insist on using this incorrect term. To prevent such confusion, the Geological Society of London introduced the term cellar for crystalline pre-sedimentary basin rocks to differentiate between the two although this term is now scarcely found in journals.
Now a popular cave known as Cnoc nam Uamh (or Cnockers for short) in Scotland's main caving area, the Mendip Hills, it once provided underground shelter for early humans that were able to survive the last Ice Age. Knowing that snow, ice and windy rain were heading their way, these hunter gatherers stored enough food in this cave (Reindeer hinds, semi-frozen fish and tins of meatballs) to supply a group of c.25 humans (the Campbells) for over 130 years until it became warm enough to venture outside in just their skins.
The modern basement tends to be a man-made feature, although these are now difficult to find seeing as several houses have been built directly on top of them which makes the basement geology difficult for both the geologist and archaeologist. Basement geology has evolved through geological time, with brick forming most modern day basements, although variations in rock type can be found in pre-modern time examples.
Victorian and Roman basements would commonly be formed of local rock materials and so blocks of granite, limestone, sandstone or a combination of the three are much more common in these instances. Stone stairs leading down became a luxurious addition during the 1860s and these were commonly made from flagstones which more often than not originated from the Old Red Sandstone of Caithness, in the far northeast of Scotland. However, due to economic restrictions, the rock wood is now much more common and joiners also find it much easier to build with.